Collagen is a protein that forms the major part of extracellular matrixes. Under normal physiological conditions, collagen can undergo a spontaneous self-assembly reaction and then form fibrous structures. This self assembly reaction is an entropy-driven process and is influenced by the effective charges on the collagen molecules, which is termed fibrillogenesis. Collagen has various advantages as a biomaterial, such as excellent biocompatibility and weak antigenicity, and is widely used as a carrier system for the delivery of drugs, proteins and genes. So far, the collagen matrices prepared have usually been limited to the fibrillar structural forms. Collagen-based micro-particles have demonstrated their usefulness as a sustained release medium for antimicrobial agents or as a parental carrier for cytotoxic reagents or gene delivery.
Nanoparticles show unique physical and chemical properties that are different from those of the conventional materials due to their ultra-fine size and being at a subcellular level. Nanoparticles can have increased surface area, high adsorptive capacity, and other properties associated with smaller particles, such as smaller size and mass. The nano scale size range can provide a dimension that is conducive to physico-physiological phenomena and functions at a biologically compatible level.
Various chemical or physical processing techniques have been developed to manufacture nano scale particles. Among these techniques, solvent-based processes, such as emulsification-solvent evaporation, emulsification-solvent diffusion and precipitation methods, are often used to manufacture nano scale particles. Dry and wet milling processes are also widely used to reduce the particle size for the preparation of nano scale particles.